LONDON — A London restaurant is offering diners the chance to learn whether they are descended from the rampaging Mongol ruler Genghis Khan — and win a free meal if they are.

The promotion by the restaurant Shish has proved surprisingly popular, exemplifying how Genghis Khan, once reviled in the West as a tyrant, has gained new respect in his own country and among academics.

“We’ve had Mongolian people who’ve traveled across London to give us their details,” said Hugo Malik, bar manager of Shish, which is giving away one DNA test at each of its two London branches every day through Friday.

“They said, ’Granddad always used to tell us we were descended from Genghis Khan.”’

Granddad may have been right. Oxford Ancestors, the firm doing the testing, says as many as 17 million men in Central Asia share a pattern of Y chromosomes within their genetic sequences, indicating a common ancestor.

Because Genghis Khan conquered vast tracts of Asia and Europe in the 12th and 13th centuries and sired many offspring, it was assumed that the men share his genetic fingerprint.

“He was an all-conquering tribal leader,” said David Ashworth, a geneticist and chief executive of Oxford Ancestors. “He took their cities, he took their land, he took their women.”

Because there are no known tissue samples from Genghis Khan, the genetic tests are based on an assessment of probabilities.

Boom in bioarchaeology
The tests are part of the burgeoning field of bioarchaeology, which uses biological techniques to learn about ancient ancestors. Oxford Ancestors, founded four years ago by Oxford University geneticist Bryan Sykes, offers DNA testing to people seeking to trace their genetic roots.

Sykes believes DNA testing can map humanity’s common ancestry. In 1994, he extracted genetic samples from the Iceman, a frozen 5,000-year-old corpse found in the Tyrolean Alps, and identified a woman in Britain as his descendant.

For $330, Oxford Ancestors will tell customers which maternal clan they belong to. The Genghis Khan test is part of a plan to do the same for paternal ancestry by mapping patterns of Y chromosomes, the genetic material handed down from fathers to sons that changes little over generations.

Women have two X chromosomes, while men carry one X chromosome and one Y — so only men can take the Genghis Khan test.

“At certain markers on the Y chromosome, if it matches the Genghis Khan pattern, then on the balance of probability you are descended from the Great Khan,” Ashworth said.

What's in a Mongolian name?
Shish, which specializes in grilled kebabs, said it was offering the tests to honor Mongolia’s decision to reintroduce surnames.

In the 1990s, Mongolia’s democratic government decided to reverse a 70-year-old policy that banned surnames in hopes of breaking the power of feudal clans. By June 30, more than half the population had chosen the name Borjigin, or Master of the Blue Wolf — Genghis Khan’s clan name.

It was the latest step in the rehabilitation of the Mongol ruler.

Reviled in the West as a bloodthirsty conqueror and condemned in communist Mongolia as a symbol of a backward past, Genghis Khan is now celebrated by Mongolians as the father of their nation.

Many Western academics also have reassessed his legacy, recasting him as a brilliant military tactician, innovative ruler and early globalizer whose empire, at one point stretching from the Sea of Japan to the Danube, saw an unprecedented mingling of goods and cultures.

Genghis Khan’s descendants should “feel a sense of pride that they are descended from such a successful leader of men,” Ashworth said.

“These ancient conquerors lived in a very different world to us, and where they got was because of their own hard work. We can’t really judge them morally.”